AP Statistics : How to find confidence intervals for a proportion

Study concepts, example questions & explanations for AP Statistics

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Example Questions

Example Question #11 : Confidence Intervals

A health insurance executive suspects that 50% of the Affordable Care Act applications are incomplete (i.e. critical data is missing from the application). He wants to gather a sample to estimate the true proportion. He wants to be within 5% of the true mean with 95% confidence.

What sample size does he need?

Possible Answers:

365

395

375

385

405

Correct answer:

385

Explanation:

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